The invention relates to methods and apparatus for testing wells.
After a wellbore has been drilled, testing (e.g., drillstem testing or production testing) may be performed to determine the nature and characteristics of one or more zones of a formation before the well is completed. Characteristics that are tested for include the permeability of a formation, volume and pressure of a reservoir in the formation, fluid content of the reservoir, and other characteristics. To obtain the desired data, fluid samples may be taken as well as measurements made with downhole sensors and other instruments.
One type of testing that may be performed is a closed-chamber drillstem test. In a closed-chamber test, the well is closed in at the surface when producing from the formation under test. Instruments may be positioned downhole and at the surface to make measurements. One advantage offered by closed-chamber testing is that hydrocarbons and other well fluids are not produced to the surface during the test. This alleviates some of the environmental concerns associated with having to burn off or otherwise dispose of hydrocarbons that are produced to the surface. However, conventional closed-chamber testing is limited in its accuracy and completeness due to limited flow of fluids from the formation under test. The amount of fluids that can be produced from the zone under test may be limited by the volume of the closed chamber.
A further issue associated with testing a well is communication of test results to the surface. Some type of mechanism is needed to communicate collected test data to well surface equipment. One possible communications mechanism is to run an electrical cable down the wellbore to the sensors. This, however, may add to the complexity and reduce the reliability of the test string.
A need thus exists for an improved method and apparatus for testing wells.
In general, according to one embodiment, a test system for testing a well having a first zone and a second zone includes a chamber and an isolation device moveable in the chamber. The isolation device separates a first and a second portion of the chamber. The chamber is adapted to receive fluid in the second chamber portion from the first zone, the isolation device being adapted to be moved in the chamber in a first direction by the first zone fluid. The first chamber portion is chargeable with fluid pressure to move the isolation device in a second direction to pump the first zone fluid inside the second chamber portion into the second zone.
In general, in accordance with another embodiment, a test system for testing a formation in a well includes a flow conduit having a first general flow area adapted to receive fluid from the formation and a closed chamber including a tubing having a second general flow area that is greater than the first general flow area. The closed chamber is adapted to receive formation fluid from the flow conduit.
Other features and embodiments will become apparent from the following description, from the drawings, and from the claims.